Potential Peripartum Markers of Infectious-Inflammatory Complications in Spontaneous Preterm Birth

Figure 4

Global and targeted quantification techniques used for the exploratory and verification phase as demonstrated on lipocalin-1 peptide GLSTESILIPR. (a) MALDI-TOF/TOF MS/MS spectra of iTRAQ-labeled peptides were used for protein identification and (b) for global quantification based on the iTRAQ reporter ions 114–117. (c) For LC-SRM verification, a library of HCD MS/MS spectra of dimethylated peptides was compiled first. SRM transitions for each peptide were then selected based on the spectral information in the library (e.g., peptide GLSTESILIPR was quantified by fragments y₉ and ). (d) For accurate quantification, intensities of LC-SRM peaks obtained on QqQ instrument were normalized against a global internal standard (GIS) prepared by reaction of the same peptides with formaldehyde-d₂.

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